The disclosure of Japanese Patent Application No. 2000-275502 filed on Sep. 11, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a high-pressure fuel supply system for performing fuel injection to an internal combustion engine.
2. Description of Related Art
In order to perform fuel injection directly into cylinders of an internal combustion engine, it is required to supply a highly pressurized fuel or high-pressure fuel to each of fuel injection valves. A high-pressure fuel supply system employed for the aforementioned purpose is well known in the art.
A general high-pressure fuel supply system includes a delivery pipe leading to each of the fuel injection valves, a high-pressure pump for feeding the high-pressure fuel under pressure to the delivery pipe, and a low-pressure pump connected to an intake side of the high-pressure pump so as to make sure that the fuel is admitted by the high-pressure pump. Generally the low-pressure pump is of an electric power driven type, and therefore is capable of feeding the fuel under pressure at a rated discharge pressure immediately after the engine start-up. On the other hand, as the high-pressure pump is of an engine-driven type, it is not sufficiently driven immediately after the engine start-up, thus failing to feed sufficient amount of the fuel under pressure.
There have been proposed various kinds of technique to initiate fuel injection by increasing the pressure in the delivery pipe to the rated discharge pressure of the low-pressure pump (e.g., 0.3 MPa) upon the engine start-up. However, the rated discharge pressure is considerably lower than a target high fuel pressure (e.g., 12 MPa) of the delivery pipe in a normal condition. Therefore, it is difficult to initiate the fuel injection at an appropriate pressure in the delivery pipe.
In order to solve the aforementioned problem, JP-A-9-184464 discloses an accumulator type boosting mechanism. In this boosting mechanism, an accumulator that accumulates the fuel pressure during an engine operation is employed so as to increase the pressure in a high-pressure pipe to a preset starting pressure upon the engine start-up.
It is an object of the invention to provide a high-pressure fuel supply system for fuel injection of an internal combustion engine including an accumulator-type boosting mechanism with an improved structure.
A high-pressure fuel supply system is provided with an accumulator type boosting mechanism which raises a pressure of a high-pressure portion of the high-pressure fuel supply system to a predetermined starting pressure upon starting up of an internal combustion engine. The accumulator type boosting mechanism is supported on the internal combustion engine.
In the high-pressure fuel supply system, the high-pressure portion is provided with a delivery pipe which supplies a high-pressure fuel to a plurality of fuel injection valves, and the delivery pipe is supported on the plurality of fuel injection valves mounted in the internal combustion engine. The accumulator type boosting mechanism is connected to the delivery pipe at a portion near a fuel inlet.
In the high-pressure fuel supply system, the accumulator type boosting mechanism includes a gas chamber and a liquid chamber interposed between the gas chamber and a fuel in the high-pressure portion, and the gas chamber and the liquid chamber are separated by an elastically deformable diaphragm.
In the high-pressure fuel supply system, the accumulator type boosting mechanism includes a gas chamber, a fuel chamber, a communication path that allows communication between the fuel chamber and the high-pressure portion, a valve body which serves to open and close the communication path, and a solenoid which operates the valve body. The solenoid is disposed in the fuel chamber, which is utilized to raise a fuel temperature in the fuel chamber.